Not Applicable
1. Field of the Invention
The present invention relates to devices for monitoring cardiac function in animals, and more particularly to such monitoring apparatus which employ components implanted in the animal.
2. Description of the Related Art
Patients with coronary disease often require monitoring in order to detect changes in their heart function. For example, cardiologists often are interested in cardiac output which is the amount of blood pumped from the heart during each cycle. The cardiac output can be determined from detecting the change in volume as the heart contracts. In other cases, it is desirable to detect movement of various portions of the heart to determine whether the heart muscles are functioning properly.
Most procedures for monitoring cardiac activity and motion employ complex imaging of the heart using ultrasound, radio isotopes or magnetic resonance imaging apparatus and require that the patient go to a facility with the proper imaging equipment.
As a consequence, it is desirable to provide an apparatus which can monitor heart motion without the use of special facilities. There also is a desire to be able to observe blood flow through coronary arteries and monitor cardiac output on a continuous basis.
An apparatus for monitoring activity of an organ, such as the heart, in an animal comprises a transmitter for wirelessly sending an interrogation signal through the animal. One or more transponders, adapted to be attached to the organ, produce a reaction in response to receipt of the interrogation signal. In the preferred embodiment, that reaction comprises sending a reply signal wirelessly through the animal. A receiver detects the reaction of each transponder and a controller determines a characteristic of the organ based on the reaction of each transponder.
For example, the position of each transponder, and thus the position of that part of the organ at which the transponder is located, can be determined by analyzing the intensity or relative time of receipt of the reply signals. The positions of the respective transponders then can be used to derive the volume of the organ and volume changes over time can be observed as in the case of a beating heart. Sensors also may be connected to the transponders to measure a physical characteristic of the organ and send information about that characteristic via the reply signal.